The selection and elicitation of typical art and soiling material started and is in progress. We will address three main classes of CH materials/surfaces that are well represented in museum collections, but often prove extremely difficult to clean due to their porosity and/or sensitivities to water, organic solvents and mechanical abrasion and currently prove extremely problematic for treatment: (1) Porous inorganic materials, mainly used for 3D sculptural objects and architectural surfaces, such as plaster, limestone, sandstone, alabaster, cement; (2) traditional matte, powdery and water sensitive media, and mechanically sensitive painted surfaces, such as pastels, drawings, gouache, (3) modern and contemporary media, such as unvarnished modern oils, alkyd resins, acrylics, matte paint systems with insufficient binding media, waxes, synthetic resins, silicon-based materials, elastomers, experimental media.